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Multiple PWM fan adapter

If you need to get an additional fan running of your MOBO's PWM CPU Fan header, this will work, and provide monitoring of the second fan:

If you need more than one extra, you can simply 'daisy-chain' them:

PWM JEDEC spec says MOBO PWM headers 'should' supply 1.5A steady-state, and tolerate a 2.2A start-up surge. Most of the fans I've checked seem to run around .11 to .16 A, so several should be OK. Your mileage may vary. Good luck trying to find your MOBO's spec for this!

Re: Multiple PWM fan adapter

Your diagrams are nice but I'm curious how many fans one could run from a single mobo header before the thing fries? I always try to hook up all extra fans directly to the PSU to avoid the possibility of drawing too much power through the motherboard.

Re: Multiple PWM fan adapter

Artic Cooling's multi-fan FAQ says:

"In most cases, we recommend users to connect maximum 5 PWM fans. With 5 PWM fans running at full speed, the current consumption will still remain within the motherboard specification. Recent mother boards (i.e. P965) supply up to 3.0Amps current from the CPU fan socket. In this case, o­ne Arctic Fan 12 PWM fan consumes 0.13Amp during maximum speed operation. When up to 5 fans are connected: 0.13Amp x 5 = 0.65Amp. It is still far below the specification. Some older boards (i.e. i865) supply 1.8Amp current from the CPU fan socket, still sufficient enough to handle. For more information please consult your motherboard manual to obtain the maximum current your motherboard can supply to the CPU fan."

I am assuming that, as a manufacturer, Artic has access to MOBO data that I don't. I haven't done a really thorough search for specific board info, and am generalizing from the nine or ten MOBO manuals I DL'd and read in the process of eliminating the finalists for my next development system (which will be a Gb GA-X48-DQ6). I certainly could have missed something, as it's a total of more than a thousand pages of PDF's, but it seems to me that actual technical data (unless it pertains to OC'ing) is scarcer than hen's teeth. That said, though, if you think about it, the PWM spec's 1.5A seems pretty likely to be accomodated: my little 'handy cheat sheet' says I can put 1.4A through a 28Ga wire, and that's less than thirteen thousandths in diameter, or roughly two or three times the diameter of a black human hair! I don't know offhand what the current thickness of board traces is, but I would guess they have at least that cross-sectional area, and therefore at least that current capacity...

If anyone locates these spec's for THEIR MOBO, please post 'em here so we can make some better informed guesses

Re: Multiple PWM fan adapter

I am new to the list and very interested in solution to connect two CPU PWM Fans (push-pull mode) as well one or two more case fans (i.e. 2 to 4 PWM fans) onto my Gigabyte GA-EX58-UD4P motherboard's CPU Fan header. My I7 920 cpu cooler is the Prolimatech Megahalem, my case ThermalTake V9 Black Series Model VJ40001N2Z ( with 2x 120x120x25mm. 2x 230x230x20mm case fans).

Did I miss something, I do not see any diagrams referred above even after logging in?

I was also interested in the 120x120mm arctic cooling fans using an integrated PWM signal anplifier to relay across several fans, but I would like more airflow and higher static pressure out my CPU fans.

I cam across this PWM Splitter - Smart Fan Cable from Akasa (AK-CB002 cable model). I was told teh wiring is rated for at least 2A, my mobo cpu header is rated at 1A. Note how the ground and 12V are supplied to fans by the PSU using a 4 pin Molex and only the PWM signal and Tachometer are used from mobo cpu PWM header. Akasa Thermal Solution

Anyone has used this Akasa PWM - splitter cable and or fans for their system. Note that by connecting two cables together one could connect not just three but 5 PWM fans.

Re: Multiple PWM fan adapter

The neat thing about PWM fans is that you can supply the 12V straight from the PSU and attach the PWM signal wire to the motherboard header. This allows you to control many fans from one motherboard header without worrying about current draw.

You may still run into problems if you use upwards of 6 - 8 fans due to the fact that the PWM signal will get weaker the more fans you attach. This is why the arctic cooling fans use a PWM amplifier.

Re: Multiple PWM fan adapter

Both worked fine, same speed and all. Akasa splitter definitely comes in handy in many situations. Note that when using cpu header, the speeds were the same for all fans, no variations due to weakening PWM signal, so the PWM amplifier thing def. works =)

AC fans are quiet enough, but the spinning range sucks. On my 3.7ghz i7 920, they spin from 1200RPM to 1300 (1.31vcore). I am considering buying fans with a wider spinning range.